### What is Urticaria Pigmentosa? Urticaria Pigmentosa is a type of rash that mostly affects children and young adults. It appears as reddish-brown spots on the skin that can form hives or blisters when rubbed. This reaction is known as Darier's sign. ### Causes The condition is caused by a build-up of mast cells in the skin. Mast cells are part of the immune system and release histamine when they detect germs. The abnormal build-up happens due to a genetic mutation, usually occurring in the womb but not inherited from parents. ### Symptoms - Reddish-brown spots on the skin - Hives or blisters when the spots are rubbed (Darier's sign) - Itchiness and swelling ### Diagnosis The rash is so specific that doctors can usually diagnose it without further tests. However, if systemic involvement is suspected, additional tests may be needed. ### Treatment Most children outgrow the condition as they age. There is no treatment to prevent new spots, but the following can help manage symptoms: - Antihistamines to reduce itching and swelling - Avoiding triggers like certain medications, temperature changes, and stress ### Complications In rare cases, Urticaria Pigmentosa can progress to systemic mastocytosis, which can lead to severe allergic reactions and other complications. ### Conclusion While Urticaria Pigmentosa can be uncomfortable, it usually only affects the skin and often improves with age. Proper management and avoiding triggers can help control symptoms.